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8223777: In posix_spawn mode, failing to exec() jspawnhelper does not result in an error

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Reviewed-by: rriggs, martin, fweimer
This commit is contained in:
Thomas Stuefe 2019-06-05 09:12:45 +02:00
parent 858b7e21d6
commit d45aa9c1a9
3 changed files with 51 additions and 0 deletions
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36
src/java.base/unix/native/libjava/ProcessImpl_md.c
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@ -655,6 +655,18 @@ Java_java_lang_ProcessImpl_forkAndExec(JNIEnv *env,
c->redirectErrorStream = redirectErrorStream;
c->mode = mode;
/* In posix_spawn mode, require the child process to signal aliveness
* right after it comes up. This is because there are implementations of
* posix_spawn() which do not report failed exec()s back to the caller
* (e.g. glibc, see JDK-8223777). In those cases, the fork() will have
* worked and successfully started the child process, but the exec() will
* have failed. There is no way for us to distinguish this from a target
* binary just exiting right after start.
*
* Note that we could do this additional handshake in all modes but for
* prudence only do it when it is needed (in posix_spawn mode). */
c->sendAlivePing = (mode == MODE_POSIX_SPAWN) ? 1 : 0;
resultPid = startChild(env, process, c, phelperpath);
assert(resultPid != 0);
@ -674,6 +686,30 @@ Java_java_lang_ProcessImpl_forkAndExec(JNIEnv *env,
}
close(fail[1]); fail[1] = -1; /* See: WhyCantJohnnyExec (childproc.c) */
/* If we expect the child to ping aliveness, wait for it. */
if (c->sendAlivePing) {
switch(readFully(fail[0], &errnum, sizeof(errnum))) {
case 0: /* First exec failed; */
waitpid(resultPid, NULL, 0);
throwIOException(env, 0, "Failed to exec spawn helper.");
goto Catch;
case sizeof(errnum):
assert(errnum == CHILD_IS_ALIVE);
if (errnum != CHILD_IS_ALIVE) {
/* Should never happen since the first thing the spawn
* helper should do is to send an alive ping to the parent,
* before doing any subsequent work. */
throwIOException(env, 0, "Bad code from spawn helper "
"(Failed to exec spawn helper.");
goto Catch;
}
break;
default:
throwIOException(env, errno, "Read failed");
goto Catch;
}
}
switch (readFully(fail[0], &errnum, sizeof(errnum))) {
case 0: break; /* Exec succeeded */
case sizeof(errnum):